/*
 * The Apache Software License, Version 1.1
 *
 *
 * Copyright (c) 2001-2003 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Axis" and "Apache Software Foundation" must
 *    not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    nor may "Apache" appear in their name, without prior written
 *    permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */
package com.kenai.jbosh;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.Serializable;

/**
 * <code>QName</code> class represents the value of a qualified name as
 * specified in <a href="http://www.w3.org/TR/xmlschema-2/#QName">XML Schema
 * Part2: Datatypes specification</a>.
 * <p>
 * The value of a QName contains a <b>namespaceURI</b>, a <b>localPart</b> and a
 * <b>prefix</b>. The localPart provides the local part of the qualified name.
 * The namespaceURI is a URI reference identifying the namespace.
 * 
 * @version 1.1
 */
public class QName implements Serializable {

	/** comment/shared empty string */
	private static final String emptyString = "".intern();

	/** Field namespaceURI */
	private String namespaceURI;

	/** Field localPart */
	private String localPart;

	/** Field prefix */
	private String prefix;

	/**
	 * Constructor for the QName.
	 * 
	 * @param localPart
	 *            Local part of the QName
	 */
	public QName(String localPart) {
		this(emptyString, localPart, emptyString);
	}

	/**
	 * Constructor for the QName.
	 * 
	 * @param namespaceURI
	 *            Namespace URI for the QName
	 * @param localPart
	 *            Local part of the QName.
	 */
	public QName(String namespaceURI, String localPart) {
		this(namespaceURI, localPart, emptyString);
	}

	/**
	 * Constructor for the QName.
	 * 
	 * @param namespaceURI
	 *            Namespace URI for the QName
	 * @param localPart
	 *            Local part of the QName.
	 * @param prefix
	 *            Prefix of the QName.
	 */
	public QName(String namespaceURI, String localPart, String prefix) {
		this.namespaceURI = (namespaceURI == null) ? emptyString : namespaceURI
				.intern();
		if (localPart == null) {
			throw new IllegalArgumentException("invalid QName local part");
		} else {
			this.localPart = localPart.intern();
		}

		if (prefix == null) {
			throw new IllegalArgumentException("invalid QName prefix");
		} else {
			this.prefix = prefix.intern();
		}
	}

	/**
	 * Gets the Namespace URI for this QName
	 * 
	 * @return Namespace URI
	 */
	public String getNamespaceURI() {
		return namespaceURI;
	}

	/**
	 * Gets the Local part for this QName
	 * 
	 * @return Local part
	 */
	public String getLocalPart() {
		return localPart;
	}

	/**
	 * Gets the Prefix for this QName
	 * 
	 * @return Prefix
	 */
	public String getPrefix() {
		return prefix;
	}

	/**
	 * Returns a string representation of this QName
	 * 
	 * @return a string representation of the QName
	 */
	public String toString() {

		return ((namespaceURI == emptyString) ? localPart : '{' + namespaceURI
				+ '}' + localPart);
	}

	/**
	 * Tests this QName for equality with another object.
	 * <p>
	 * If the given object is not a QName or is null then this method returns
	 * <tt>false</tt>.
	 * <p>
	 * For two QNames to be considered equal requires that both localPart and
	 * namespaceURI must be equal. This method uses <code>String.equals</code>
	 * to check equality of localPart and namespaceURI. Any class that extends
	 * QName is required to satisfy this equality contract.
	 * <p>
	 * This method satisfies the general contract of the
	 * <code>Object.equals</code> method.
	 * 
	 * @param obj
	 *            the reference object with which to compare
	 * 
	 * @return <code>true</code> if the given object is identical to this QName:
	 *         <code>false</code> otherwise.
	 */
	public final boolean equals(Object obj) {

		if (obj == this) {
			return true;
		}

		if (!(obj instanceof QName)) {
			return false;
		}

		if ((namespaceURI == ((QName) obj).namespaceURI)
				&& (localPart == ((QName) obj).localPart)) {
			return true;
		}

		return false;
	}

	/**
	 * Returns a QName holding the value of the specified String.
	 * <p>
	 * The string must be in the form returned by the QName.toString() method,
	 * i.e. "{namespaceURI}localPart", with the "{namespaceURI}" part being
	 * optional.
	 * <p>
	 * This method doesn't do a full validation of the resulting QName. In
	 * particular, it doesn't check that the resulting namespace URI is a legal
	 * URI (per RFC 2396 and RFC 2732), nor that the resulting local part is a
	 * legal NCName per the XML Namespaces specification.
	 * 
	 * @param s
	 *            the string to be parsed
	 * @throws java.lang.IllegalArgumentException
	 *             If the specified String cannot be parsed as a QName
	 * @return QName corresponding to the given String
	 */
	public static QName valueOf(String s) {

		if ((s == null) || s.equals("")) {
			throw new IllegalArgumentException("invalid QName literal");
		}

		if (s.charAt(0) == '{') {
			int i = s.indexOf('}');

			if (i == -1) {
				throw new IllegalArgumentException("invalid QName literal");
			}

			if (i == s.length() - 1) {
				throw new IllegalArgumentException("invalid QName literal");
			} else {
				return new QName(s.substring(1, i), s.substring(i + 1));
			}
		} else {
			return new QName(s);
		}
	}

	/**
	 * Returns a hash code value for this QName object. The hash code is based
	 * on both the localPart and namespaceURI parts of the QName. This method
	 * satisfies the general contract of the <code>Object.hashCode</code>
	 * method.
	 * 
	 * @return a hash code value for this Qname object
	 */
	public final int hashCode() {
		return namespaceURI.hashCode() ^ localPart.hashCode();
	}

	/**
	 * Ensure that deserialization properly interns the results.
	 * 
	 * @param in
	 *            the ObjectInputStream to be read
	 */
	private void readObject(ObjectInputStream in) throws IOException,
			ClassNotFoundException {
		in.defaultReadObject();

		namespaceURI = namespaceURI.intern();
		localPart = localPart.intern();
		prefix = prefix.intern();
	}
}
